1. Field of the Invention
The invention relates to a fuel cell.
2. Description of Related Art
A fuel cell usually has a stack structure in which a plurality of single cells that serve as power generating elements are stacked. Reaction gases flow into gas flow passages, provided for each single cell, via respective manifolds and are supplied to a power generating portion of each single cell. However, if the gas flow passages of part of the single cells are blocked by frozen water content, or the like, the amounts of reaction gases supplied to the part of the single cells become insufficient, so the part of the single cells may possibly generate negative voltage. In this way, when the operation of the fuel cell is continued in a state where part of the single cells generate negative voltage, not only the power generation performance of the fuel cell overall deteriorates but also the electrodes of those single cells may possibly degrade. To take measures against the above problems, for example, like the techniques described in Japanese Patent Application Publication No. 2005-093111 (JP-A-2005-093111), Japanese Patent Application Publication No. 2004-031232 (JP-A-2004-031232) and Japanese Patent Application Publication No. 2007-265929 (JP-A-2007-265929), various techniques for suppressing deterioration of the power generation performance of a fuel cell or degradation of a fuel cell due to such negative voltage have been suggested so far.